Endoscopic instruments are often used in gastroenterology or cardiac surgery, and such instruments are normally introduced through an endoscope working channel, with the endoscope in turn introduced through a lumen within the patient's body. These instruments are therefore of a relatively small size, often no more than 5 mm in diameter. They are deployed at the end of a relatively long flexible shaft, such that they can be maneuvered within a lumen as described above.
Where such instruments include the deployment of one component relative to another, such deployment is often carried out by sliding one handle component relative to another. The components are often supplied with loops or moulded surfaces adapted to be contacted by the fingers and thumb of the user of the instrument. One instrument of this type is described in U.S. Pat. No. 5,290,286 in which a component is movable within a housing, the movable component being provided with a thumb ring and the housing with finger loops. The present invention attempts to provide an improvement to endoscopic instruments of this type.